Allow DND of tabs among viewspaces

BUG: 426768

kate/CMakeLists.txt

@@ -92,6 +92,7 @@ target_sources(
     kateviewmanager.cpp
     kateviewspace.cpp
     katewaiter.cpp
+    tabmimedata.cpp
 
     katecommandbar.cpp
     commandmodel.cpp

kate/katetabbar.cpp

@@ -8,12 +8,17 @@
 
 #include "katetabbar.h"
 #include "kateapp.h"
+#include "tabmimedata.h"
 
+#include <QApplication>
+#include <QDrag>
 #include <QIcon>
 #include <QMimeData>
 #include <QPainter>
+#include <QPixmap>
 #include <QResizeEvent>
 #include <QStyleOptionTab>
+#include <QStylePainter>
 #include <QWheelEvent>
 
 #include <KAcceleratorManager>
@@ -160,6 +165,13 @@ void KateTabBar::mousePressEvent(QMouseEvent *event)
     if (!isActive()) {
         Q_EMIT activateViewSpaceRequested();
     }
+
+    if (event->button() == Qt::LeftButton && tabAt(event->pos()) != -1) {
+        dragStartPos = event->pos();
+    } else {
+        dragStartPos = {};
+    }
+
     QTabBar::mousePressEvent(event);
 
     // handle close for middle mouse button
@@ -171,6 +183,59 @@ void KateTabBar::mousePressEvent(QMouseEvent *event)
     }
 }
 
+void KateTabBar::mouseMoveEvent(QMouseEvent *event)
+{
+    if (dragStartPos.isNull()) {
+        QTabBar::mouseMoveEvent(event);
+        return;
+    }
+
+    if ((event->pos() - dragStartPos).manhattanLength() < QApplication::startDragDistance()) {
+        QTabBar::mouseMoveEvent(event);
+        return;
+    }
+
+    if (rect().contains(event->pos())) {
+        return QTabBar::mouseMoveEvent(event);
+    }
+
+    QDrag *drag = new QDrag(this);
+
+    int tab = tabAt(dragStartPos);
+    QRect rect = tabRect(tab);
+
+    QPixmap p(rect.size());
+    p.setDevicePixelRatio(this->devicePixelRatioF());
+    p.fill(Qt::transparent);
+
+    // For some reason initStyleOption with tabIdx directly
+    // wasn't working, so manually set some stuff
+    QStyleOptionTabV4 opt;
+    initStyleOption(&opt, 0);
+    opt.text = tabText(tab);
+    opt.state = QStyle::State_Selected | QStyle::State_Raised;
+    opt.tabIndex = tab;
+    opt.features = QStyleOptionTab::TabFeature::HasFrame;
+
+    QStylePainter paint(&p, this);
+    paint.drawControl(QStyle::CE_TabBarTab, opt);
+    paint.end();
+
+    auto parentViewSpace = qobject_cast<KateViewSpace *>(parentWidget());
+    Q_ASSERT(parentViewSpace);
+
+    auto mime = new TabMimeData(parentViewSpace, tabDocument(tab), tab);
+    drag->setMimeData(mime);
+    drag->setPixmap(p);
+    QPoint hp;
+    hp.setX(dragStartPos.x() - rect.x());
+    drag->setHotSpot(hp);
+
+    dragStartPos = {};
+
+    drag->exec();
+}
+
 void KateTabBar::contextMenuEvent(QContextMenuEvent *ev)
 {
     int id = tabAt(ev->pos());

kate/katetabbar.h

@@ -122,6 +122,8 @@ protected:
     //! Override to request making the tab bar active.
     void mousePressEvent(QMouseEvent *event) override;
 
+    void mouseMoveEvent(QMouseEvent *) override;
+
     //! Request context menu
     void contextMenuEvent(QContextMenuEvent *ev) override;
 
@@ -167,6 +169,8 @@ private:
      * is a bit strange tab replacement a few times
      */
     std::unordered_map<KTextEditor::Document *, std::pair<quint64, bool>> m_docToLruCounterAndHasTab;
+
+    QPoint dragStartPos;
 };
 
 #endif // KATE_TAB_BAR_H

kate/kateviewmanager.cpp

@@ -783,6 +783,15 @@ void KateViewManager::closeView(KTextEditor::View *view)
     }
 }
 
+void KateViewManager::moveViewToViewSpace(KateViewSpace *dest, KateViewSpace *src, KTextEditor::Document *doc)
+{
+    // We always have an active view at this point which is what we are moving
+    Q_ASSERT(activeView());
+    auto view = src->takeView(doc);
+    dest->addView(view);
+    setActiveSpace(dest);
+}
+
 void KateViewManager::splitViewSpace(KateViewSpace *vs, // = 0
                                      Qt::Orientation o) // = Qt::Horizontal
 {

kate/kateviewmanager.h

@@ -75,6 +75,8 @@ public:
     void closeView(KTextEditor::View *view);
     KateMainWindow *mainWindow();
 
+    void moveViewToViewSpace(KateViewSpace *dest, KateViewSpace *src, KTextEditor::Document *doc);
+
 private Q_SLOTS:
     void activateView(KTextEditor::View *view);
     void activateSpace(KTextEditor::View *v);

kate/kateviewspace.cpp

@@ -15,6 +15,7 @@
 #include "katesessionmanager.h"
 #include "kateupdatedisabler.h"
 #include "kateviewmanager.h"
+#include "tabmimedata.h"
 #include <KActionCollection>
 
 #include <KAcceleratorManager>
@@ -26,6 +27,7 @@
 #include <QHelpEvent>
 #include <QMenu>
 #include <QMessageBox>
+#include <QRubberBand>
 #include <QStackedWidget>
 #include <QToolButton>
 #include <QToolTip>
@@ -129,11 +131,16 @@ KateViewSpace::KateViewSpace(KateViewManager *viewManager, QWidget *parent, cons
 
     connect(this, &KateViewSpace::viewSpaceEmptied, m_viewManager, &KateViewManager::onViewSpaceEmptied);
 
+    // we accept drops (tabs from other viewspaces / windows)
+    setAcceptDrops(true);
+
     // init the bars...
     statusBarToggled();
     tabBarToggled();
 }
 
+KateViewSpace::~KateViewSpace() = default;
+
 bool KateViewSpace::eventFilter(QObject *obj, QEvent *event)
 {
     QToolButton *button = qobject_cast<QToolButton *>(obj);
@@ -397,6 +404,7 @@ void KateViewSpace::registerDocument(KTextEditor::Document *doc)
     connect(m_tabBar, &KateTabBar::currentChanged, this, &KateViewSpace::changeView);
 }
 
+
 void KateViewSpace::closeDocument(KTextEditor::Document *doc)
 {
     // If this is the only view of the document,
@@ -423,6 +431,64 @@ void KateViewSpace::closeDocument(KTextEditor::Document *doc)
     }
 }
 
+void KateViewSpace::dragEnterEvent(QDragEnterEvent *e)
+{
+    auto mimeData = qobject_cast<const TabMimeData *>(e->mimeData());
+    if (mimeData && this != mimeData->sourceVS && !hasDocument(mimeData->doc)) {
+        m_dropIndicator.reset(new QRubberBand(QRubberBand::Rectangle, this));
+        m_dropIndicator->setGeometry(rect());
+        m_dropIndicator->show();
+        e->acceptProposedAction();
+        return;
+    }
+    QWidget::dragEnterEvent(e);
+}
+
+void KateViewSpace::dragLeaveEvent(QDragLeaveEvent *e)
+{
+    m_dropIndicator.reset();
+    QWidget::dragLeaveEvent(e);
+}
+
+void KateViewSpace::dropEvent(QDropEvent *e)
+{
+    if (auto mimeData = qobject_cast<const TabMimeData *>(e->mimeData())) {
+        m_viewManager->moveViewToViewSpace(this, mimeData->sourceVS, mimeData->doc);
+        m_dropIndicator.reset();
+        e->accept();
+        return;
+    }
+    QWidget::dropEvent(e);
+}
+
+bool KateViewSpace::hasDocument(KTextEditor::Document *doc) const
+{
+    return m_registeredDocuments.contains(doc) && (m_docToView.find(doc) != m_docToView.end());
+}
+
+KTextEditor::View *KateViewSpace::takeView(KTextEditor::Document *doc)
+{
+    auto it = m_docToView.find(doc);
+    if (it == m_docToView.end()) {
+        return nullptr;
+    }
+    auto *view = it->second;
+    stack->removeWidget(view);
+    m_tabBar->removeDocument(doc);
+    documentDestroyed(doc);
+    return view;
+}
+
+void KateViewSpace::addView(KTextEditor::View *v)
+{
+    registerDocument(v->document());
+    m_docToView[v->document()] = v;
+    // We must not already have this widget
+    Q_ASSERT(stack->indexOf(v) == -1);
+    stack->addWidget(v);
+    showView(v);
+}
+
 void KateViewSpace::documentDestroyed(QObject *doc)
 {
     /**

kate/kateviewspace.h

@@ -31,6 +31,8 @@ class KateViewSpace : public QWidget
 public:
     explicit KateViewSpace(KateViewManager *, QWidget *parent = nullptr, const char *name = nullptr);
 
+    ~KateViewSpace();
+
     /**
      * Returns \e true, if this view space is currently the active view space.
      */
@@ -82,6 +84,24 @@ public:
      */
     void closeDocument(KTextEditor::Document *doc);
 
+    /*
+     * Does this viewspace contain @p doc
+     */
+    bool hasDocument(KTextEditor::Document *doc) const;
+
+    /**
+     * Removes @p doc from this space and returns the associated
+     * view
+     * Used for dnd
+     */
+    KTextEditor::View *takeView(KTextEditor::Document *doc);
+
+    /**
+     * Adds @p view to this space
+     * Used for dnd to add a view from another viewspace
+     */
+    void addView(KTextEditor::View *v);
+
     /**
      * Event filter to catch events from view space tool buttons.
      */
@@ -146,6 +166,12 @@ public:
     void addPositionToHistory(const QUrl &url, KTextEditor::Cursor, bool calledExternally = false);
 
     // END Location History Stuff
+protected:
+    // DND
+    void dragEnterEvent(QDragEnterEvent *e) override;
+    void dragLeaveEvent(QDragLeaveEvent *e) override;
+    void dropEvent(QDropEvent *e) override;
+
 Q_SIGNALS:
     void viewSpaceEmptied(KateViewSpace *vs);
 
@@ -256,6 +282,9 @@ private:
     // go forward in history button (only visible when the tab bar is visible)
     QToolButton *m_historyForward;
 
+    // rubber band to indicate drag and drop
+    std::unique_ptr<class QRubberBand> m_dropIndicator;
+
     friend class LocationHistoryTest;
 };
 

kate/tabmimedata.cpp

+#include "tabmimedata.h"
+
+TabMimeData::TabMimeData(KateViewSpace *vs, KTextEditor::Document *d, int sourceTabIdx)
+    : QMimeData()
+    , sourceVS(vs)
+    , doc(d)
+    , tabIdx(sourceTabIdx)
+{
+}

kate/tabmimedata.h

+#ifndef KATE_TAB_MIME_DATA_H
+#define KATE_TAB_MIME_DATA_H
+
+#include <QMimeData>
+
+#include "kateviewspace.h"
+
+namespace KTextEditor
+{
+class Document;
+}
+
+class TabMimeData : public QMimeData
+{
+    Q_OBJECT
+public:
+    TabMimeData(KateViewSpace *vs, KTextEditor::Document *d, int sourceTabIdx);
+
+    KateViewSpace *const sourceVS;
+    KTextEditor::Document *const doc;
+    const int tabIdx;
+};
+
+#endif